Public Certificate to setup external SSL Trust to Web Dispatcher

We've setup a Web Dispatcher in our DMZ to enable Fiori to connect through our firewall to a backend Gateway System. When we run https://fiori.abc.com to hit that DMZ server it needs a certificate for *.abc.com that says that site can be trusted and has been signed by a Certificate Authority. My company uses COMODO RSA to do that signing. I have their three crt's for setting this up:

AddTrustExternalCARoot.crt
COMODORSAAddTrustCA.crt
COMODORSAOrganizationValidationSecureServerCA.crt

I've tried every sapgenpse import_own_cert method I can think of and none of them work. They all seem to conflict with my Old Certificate in the PSE. I get the error, "No certificate with your public key found in supplied input". That Old Certificate has CN=<FQHN> in it.

Does anyone have an example of how to setup COMODO with sapgenpse?

Do I use the Server PSE (SAPSSLS.pse) or the Client PSE (SAPSSLC.pse)?